1. Technical Field
The present disclosure relates to a light source. More particularly, the present disclosure relates to a light source that is installed in an exposure apparatus which is used in processes of manufacturing a semiconductor, a liquid crystal substrate, a color filter, and the like.
2. Related Art
In the processes of manufacturing the semiconductors, the liquid crystal substrate, the color filter, and the like, a decrease in process time and one-shot exposure of an object to be processed which has a large area has been required. In order to cope with this requirement, a high-pressure discharge lamp has been proposed in which a larger ultraviolet radiation intensity can be obtained by applying a higher input electric power.
The input electric power to the high-pressure discharge lamp may be set to be high. In this case, problems arise in that the load to the electrodes increases and substances evaporated from the electrodes cause the high-pressure lamp to become dark and shorten the lifetime of the lamp.
FIG. 16 is a diagram illustrating a light source disclosed in JP-A-61-193358.
As shown in the drawing, in order to solve the above problems, a light source 100 is configured as follows. An electrodeless discharge chamber 104 is disposed inside an elliptical reflection mirror 101. Through a hole 102 that is provided on the side surface of the elliptical reflection mirror 101, laser light enters the discharge chamber 104, and a discharge gas enclosed in the discharge chamber is excited, so that light is emitted. According to the light source 100, it is possible to solve the above problems since electrodes are not provided in the discharge chamber 104.
However, in the light source 100 disclosed in JP-A-61-193358, the hole 102 for light incidence of the laser light and a hole 103 for light exit of the laser light are provided on the side surfaces of the elliptical reflection mirror 101. Since the holes 102 and 103 are provided on a reflective surface of the elliptical reflection mirror 101, when ultraviolet light emitted from the electrodeless discharge chamber 104 is collected by the elliptical reflection mirror 101, there is a problem in that it is very difficult to utilize the ultraviolet light efficiently. Further, since the laser light enters the electrodeless discharge chamber 104 in a direction intersecting an optical axis X of the elliptical reflection mirror 101, the discharge is extended in a horizontal direction (the direction intersecting the optical axis X), and thus is generated in a region deviating from a focal point of the elliptical reflection mirror 101. Thus, the ultraviolet light is not accurately reflected. As a result, the problem arises in that it is difficult to utilize the ultraviolet light efficiently.
Meanwhile, FIG. 17 is a diagram illustrating a light source disclosed in U.S. Patent Application Pub. US2007/0228300.
As shown in the drawing, in order to solve the above-mentioned problem, a light source 200 is configured as follows. An electrodeless discharge lamp is disposed in a reflection mirror 201. Through an opening 202 that is provided on the top of the reflection mirror 201, laser light enters a discharge chamber 203 of the discharge lamp, and a discharge gas enclosed in the discharge chamber 203 is excited, so that light is emitted. By using the light source 200, it is possible to solve the problems since electrodes are not provided in the discharge lamp.
However, also in the light source 200 disclosed in US2007/0228300, the laser light enters (passes) the reflection mirror 201 through the top opening 202 of the reflection mirror 201, and is irradiated to the discharge chamber 203, so that discharge 204 is generated. However, a part of the laser light passes through the discharge 204 and the discharge chamber 203, and thus the laser light is irradiated onto a surface to be irradiated together with light emitted from the discharge. Therefore, the laser light gives damage to a surface of an object to be processed.
FIGS. 18 and 19 are diagrams illustrating configurations for solving the above-mentioned problems of the light source 200 disclosed in US2007/0228300.
In the configuration shown in FIG. 18, the laser light, which passes through the opening for light exit from the reflection mirror 205, is reflected by the reflection mirror 206, and is irradiated into the reflection mirror 205. Thus, the discharge gas filled in the reflection mirror 205 is excited, so that discharge is generated. Light emitted by the discharge passes through the reflection mirror 206 and is output to the outside. Further, in the configuration shown in FIG. 19, the laser light, which passes through the opening for light exit from the reflection mirror 205, passes through the reflection mirror 208, and is irradiated into the reflection mirror 205. Thus, the discharge gas filled in the reflection mirror 205 is excited, so that discharge is generated. Light emitted by the discharge is reflected by the reflection mirror 208 and is output to the outside.
According to the configurations shown in FIGS. 18 and 19, it is possible to solve the above-mentioned problems of the light source shown in FIG. 17. However, in the configurations of FIGS. 18 and 19, the reflection mirrors 206 and 208 are required to have a function of wavelength selectivity, but it is difficult to manufacture them. Also, the mirrors might select wavelengths inaccurately. Additionally, in the case of the reflection mirror 206, a part of the emitted light is absorbed by the reflection mirror 206, and, similarly in the case of the reflection mirror 208, a part of the emitted light is absorbed by the reflection mirror 208. Therefore, there is a problem in that it is difficult to use the emitted light efficiently.